One of the most important requirements of a next generation wireless communication system is to support a high data rate. For this, various techniques such as multiple input multiple output (MIMO), cooperative multiple point transmission (CoMP), relay, etc., have been under research, but the most fundamental and reliable solution is to increase a bandwidth.
However, a frequency resource is in a saturation state at present, and various schemes are partially used in a wide frequency band. For this reason, in order to ensure a broadband bandwidth to satisfy a required higher data rate, a system is designed such that a basic requirement which allows separate bands to operate respective independent systems is satisfied, and a carrier aggregation (CA) is introduced. In concept, the CA aggregates a plurality of bands into one system. In this case, a band that can be independently managed is defined as a component carrier (CC).
To support growing transmission capacity, it is considered in the latest communication standard (e.g., 3GPP LTE-A or 802.16m) to expand its bandwidth to 20 MHz or higher. In this case, a wideband is supported by aggregating one or more CCs. For example, if one CC corresponds to a bandwidth of 5 MHz, four carriers are aggregated to support a bandwidth of up to 20 MHz. A system supporting carrier aggregation in this manner is called a carrier aggregation system.
The conventional carrier aggregation system uses a structure in which one control channel corresponds to one data channel. That is, one physical downlink shared channel (PDSCH) and/or one physical uplink shared channel (PUSCH) are scheduled through one physical downlink control channel (PDCCH). However, a more effective scheduling method is required since a next-generation communication system may request real-time data communication and large-volume high-speed data transmission.